Optical scanning systems incorporating scanning mirrors are generally classified into two categories, namely scanners in which the scanning mirror is located between the imaging lens and the object plane, and scanners in which the scanning mirror is located between the imaging lens and its focal plane.
Scanning systems of the first category are generally regarded as more cumbersome as they increase the overall size of the imaging system. Moreover the size of the scanning mirror is determined by the dimensions of the imaging lens aperture and the scanning geometry. In some applications such as the scanning of flat documents, it is necessary to maintain focus over the entire field of view. One such scanning system is described in U.S. Pat. No. 5,058,968 to Stark.
Scanning systems of the second category tend to be more compact as they are designed to operate within the enclosed space of the imaging system. Such systems either translate an imaging detector in the focal plane of the optic such as backplane scanners, or scan the field of view using a mirror situated between the optical lens and the image (focal) plane. One such scanning system is described in U.S. Pat. No. 5,416,609. A commercially available system of this category is the DPCS 3000, marketed by Minolta.
Backplane scanner systems of the second category translate detectors in the focal plane. In order for such systems to achieve acceptable image quality, they are required to maintain a high level of opto-mechanical detector translation stability and accuracies. As a result, such systems are often limited in the scanning rate which can be achieved, and utilize costly translatory scanning and servo means. Mirror scanner systems of the second category such as that described in U.S. Pat. No. 3,468,229 by Bellows, are require complicated scanner designs and implementations.
The disclosures of all publications mentioned in the specification and of the publications cited therein are hereby incorporated by reference.